The subject matter of the present invention relates to a computer workstation and stored software based method and apparatus for use in the energy industry, which is responsive to a plurality of seismic data obtained during a seismic operation performed in connection with a fault ridden earth formation, for determining a geologic relationship between a pair of intersecting faults, and, more particularly, for determining whether a pair of faults of a multitude of fault pairs in the seismic data "relate" (i.e.--intersect), and, if the pairs do relate, which fault of the pair is the major fault and which fault of the pair is the minor fault, and, once the major and minor faults of the pair of faults is determined, whether the minor fault intersects the major fault from above or below the major fault and therefore whether the minor fault is truncated below or above, respectively, the major fault.
In order to correctly build a sub-surface structural model which incorporates fault surfaces, it is necessary to first establish the relationships between intersecting fault surfaces. These fault surfaces can then be gathered into a fault framework. The intersection of each pair of faults is represented as a line in 3D space (the fault-fault intersection line). For each intersecting pair of fault surfaces, one is typically classified as the major fault in that pair, and the other is classified as the minor fault in that pair. Based on this classification, the minor fault surface is truncated against the major fault surface in some way. If the minor fault intersects the major fault from above (i.e., it is structurally higher than the major fault), then it will be truncated at every point which is structurally below the line which forms the fault fault intersection. In this case, we say "the minor fault is truncated below the major fault". However, if the minor fault intersects the major fault from below (i.e., it is structurally lower than the major fault), then it will be truncated at every point above the line which forms the fault fault intersection. In this case, we say "the minor fault is truncated above the major fault". Establishing the major/minor, above/below relationships for intersecting faults is important for to building a representative fault framework.
These fault fault relationships can be determined by a "one by one" examination of the fault surfaces within their geologic context. This process can be extremely time consuming when done manually especially in an area with very complex fault geometries. It requires: (1) determining which faults intersect, and then for each intersecting fault pair located, (2) determining the fault fault intersection line, (3) determining which fault is the major fault, (4) determining how the minor fault should be truncated against the major fault, and (5) removing the portion of the minor fault surface which should be truncated.
Conventional fault frameworks established fault relationships based on a "fault tree" structure. This requires establishing an absolute hierarchy starting with a single fault and adding faults as branches from this basic structure. This has required manual intervention in defining the fault tree hierarchy. It is also necessary to rebuild the entire hierarchy when removing or adding a single branch to the hierarchy. Again, this manual process for building a fault framework can be extremely time consuming.
Accordingly, there is a need for a novel apparatus which would automatically determine whether a pair of faults relate (i.e., intersect) and determine the relationships between the intersecting fault surfaces. Using this novel apparatus, all intersecting fault pairs could be determined automatically, and the fault fault intersection lines for each fault pair could be automatically computed and stored. In addition, this novel apparatus could automatically calculate the major/minor and above/below fault pair relationships. Once these relationships are automatically determined, the minor fault could be automatically truncated above or below the major fault in the proper manner.